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Abstract
The effects of dietary lipids on the content and release of norepinephrine and on the overflow of norepinephrine after alpha-adrenoceptor blockade with phentolamine were investigated in isolated perfused rat hearts. Pregnant rats were fed Purina Rodent Chow (reference diet) or a semisynthetic diet containing 16% (wt/wt) of either coconut oil (saturated fatty acids) or sunflower oil (unsaturated fatty acids). Neonatal pups were exposed to the diet via maternal milk and weaned rats were maintained on the same dietary lipid supplementation. Coconut oil caused a significant decrease in cardiac norepinephrine in all age groups when compared with the reference diet (p less than 0.01). Sunflower oil caused a significant increase in cardiac norepinephrine at 14 and 21 days of age when compared with coconut oil (p less than 0.05). Hearts prelabeled with [3H]norepinephrine were stimulated with supramaximal voltage (5 Hz, 2 ms duration, 300 pulses). At 14 and 21 days, coconut oil caused a significant decrease in norepinephrine release when compared with sunflower oil (p less than 0.05). The release of norepinephrine from hearts exposed to sunflower oil diet and the reference diet were comparable. These alterations in neuronal storage and exocytotic release of norepinephrine may be due to dietary-induced membrane perturbations. Phentolamine (10(-8)-10(-6) M) caused a dose-related increase in norepinephrine release following stimulation (supramaximal voltage 2.5 Hz, 150 pulses) of adult rat hearts from all dietary groups. However, the increase above control values was highest for coconut oil and lowest for sunflower oil (p less than 0.01), suggesting changes in receptor sensitivity. It appears that dietary lipid supplementation in the developing and adult rat could affect the myocardial alpha-adrenoceptor microenvironment which could cause changes in the prejunctional alpha-adrenoceptor neuronal function.
Published Version
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